1. Field of the Invention
The invention relates to a radiation-sensitive resin composition and a polymer.
2. Discussion of the Background
A semiconductor device (e.g., IC or LSI) production process utilizes microfabrication by means of lithography using a photoresist composition. Along with an increase in the degree of integration of integrated circuits, the semiconductor device production process has been required to form a sub-micrometer or quarter-micrometer fine pattern. Therefore, i-lines, KrF excimer laser light, or ArF excimer laser light having a short exposure wavelength has been used instead of g-lines. Lithography that utilizes electron beams, X-rays, or EUV light instead of excimer laser light has also been developed.
Lithography that utilizes EUV light is considered to be next-generation or third-generation patterning technology, and requires a positive-tone resist that exhibits high sensitivity and high resolution. In particular, an increase in sensitivity is very important for reducing the wafer processing time. However, when increasing the sensitivity of a positive-tone resist used for EUV light, a deterioration in resolution and nano edge roughness occurs. Therefore, development of a resist that achieves high sensitivity, high resolution, and low nano edge roughness has been strongly desired. Note that the term “nano edge roughness” refers to a phenomenon in which the edge of the resist pattern irregularly changes with respect to the substrate in the direction perpendicular to the line direction due to the properties of the resist, so that a difference occurs between the design dimensions and the actual pattern dimensions when viewed from above. The difference from the design dimensions is transferred by etching using the resist as a mask, and causes a deterioration in electrical properties. As a result, a decrease in yield occurs. In particular, it is very important to reduce the nano edge roughness when forming a fine pattern having a line width of 32 nm or less using EUV light. High sensitivity, high resolution, an excellent pattern shape, and low nano edge roughness have a trade-off relationship. It is very important to achieve these properties at the same time.
A polymer compound that includes an acryloyloxyphenylsulfonium salt as a monomer has been proposed in order to improve the sensitivity (see Japanese Patent Application Publication (KOKAI) No. 4-230645), and the above monomer may be incorporated in a base resin in order to reduce the line edge roughness when using a polyhydroxystyrene resin (see Japanese Patent Application Publication (KOKAI) No. 2005-84365).
A sulfonium salt in which the anion moiety is incorporated in the polymer main chain (e.g., polystyrenesulfonic acid) has been proposed in order to improve the sensitivity and the resist pattern shape (see Japanese Patent No. 3613491).
An acrylic acid derivative that includes a sulfonic acid anion (e.g., —CF2—SO3— group) in the side chain has been proposed (see Japanese Patent Application Publication (KOKAI) No. 2006-178317).